The present invention relates to a testing apparatus in general, and more particularly to a testing apparatus for testing of fluid-operated brake systems, particularly for brake systems of land-based vehicles. Still more particularly, the invention relates to a portable testing apparatus of this type.
It is known that the brake circuits of vehicles and of trailers must be periodically checked for safety reasons, and that many countries require a periodic examination of these brake systems by law. During such examinations the braking effectiveness is tested in percent of braking or retardation in m/sec..sup.2. In addition, however, it is important to examine the brake system and its functioning, in addition to carrying out the actual braking test with it. For example, compressed-air brake systems such as are used on trailers or the like, must undergo the following tests:
Measurement of the pressure drop when the system is filled (to determine the tightness of the system); PA1 Measurement of the pressure drop at the storage and brake cylinders under partial brake pressure; PA1 Measurement of the brake pressure at vented trailer control line (1-circuit system) or during pressure drop in the storage line (2-circuit system); PA1 Measurement of the pressure drop in the air tank during each full braking incident; PA1 Piston stroke of the brake cylinders during each full braking incident; PA1 Position of the piston rods of the brake cylinders on releasing of the brake; PA1 Measurement of the pressure in the control line of the trailer brake valve; PA1 Measurement of the response stages and the adjustability of the trailer brake valve (at pressure drop in the control line in the case of an indirectly operating trailer brake valve or at pressure increase in the brake line in the case of a direct acting trailer brake valve); PA1 Operation of the brake light switch; PA1 Measurement of the pressure at the load sensing valve for different settings; PA1 Measurement of the opening pressure of the overflow valve between two air tanks.
Analogous tests are also carried out on the self-propelled vehicles having such brake systems, for example tractors of the like.
To be able to readily test compressed air brake systems, hydraulic brake systems or combined brake systems it has been proposed to provide a movable test stand which is to be connectable with a source of air pressure that is independent of the motor vehicle to be tested. However, for various reasons it has been found that this prior-art proposal was not workable and not satisfactory, and in addition that it was very heavy and required large amounts of space and was therefore not suitable for universal application. Another disadvantage was that it was not possible for a single operator to operate the controls of the test stand as well as to be in a position to visually supervise the elements being tested on the vehicle and/or to be able to carry out adjustments on or near these elements.